Soil Mechanics Flashcards
(30 cards)
What is lateral earth pressure?
The pressure that soil exerts in the horizontal direction against a retaining structure.
What are the three types of lateral earth pressure?
At-rest, active, and passive earth pressure.
What condition leads to active earth pressure?
When the wall moves away from the soil, reducing pressure.
What condition leads to passive earth pressure?
When the wall moves toward the soil, increasing pressure.
Which coefficient is used to calculate active earth pressure?
Ka (coefficient of active earth pressure).
What is Rankine’s theory used for?
To estimate lateral earth pressures assuming a frictionless wall and horizontal backfill.
What is the difference between soil compaction and consolidation?
Compaction is the reduction of air voids; consolidation is the reduction of water in saturated soils.
What is the purpose of soil compaction?
To increase soil strength and decrease settlement.
What test is commonly used for soil compaction?
Proctor test (standard or modified).
What is the optimum moisture content?
The moisture content at which a soil reaches its maximum dry density.
What is primary consolidation?
Settlement due to the expulsion of water from voids under sustained load.
What is secondary compression?
Deformation that occurs after primary consolidation due to soil particle adjustment.
What is bearing capacity of soil?
The ability of soil to support the loads applied to the ground.
What is ultimate bearing capacity?
The maximum pressure soil can withstand before failure.
What is net safe bearing capacity?
The maximum pressure soil can bear safely, considering a factor of safety.
Name a common method for calculating bearing capacity.
Terzaghi’s bearing capacity equation.
What are the components of Terzaghi’s equation?
Cohesion, overburden pressure, and footing width (with bearing capacity factors Nc, Nq, Nγ).
What type of soil generally has higher bearing capacity: sand or clay?
Dense sand typically has higher bearing capacity than soft clay.
What is settlement in geotechnical engineering?
The downward movement of a structure due to compression of the soil beneath.
What are the three types of settlement?
Immediate, primary consolidation, and secondary compression.
What causes immediate settlement?
Elastic deformation of dry or unsaturated soil immediately after loading.
What is differential settlement?
Uneven settlement across a structure that can cause structural damage.
Which type of soil is most susceptible to consolidation settlement?
Saturated clay.
What instrument is often used to measure settlement over time?
Settlement plates or monitoring wells.
